considered to be a lack of modularity. Ideally, such data-access logic should be encapsulated within DAOs but,
unfortunately, GORM does not explicitly support them.
GORM provides an innovative style of O/R mapping that
simplifies application code. One of the key ways it does
this is by leveraging the dynamic features of the Groovy
language. GORM injects persistence-related methods
into domain classes at runtime. It eliminates a significant
amount of data-access methods and classes, while still
decoupling the business logic from the ORM framework.
GORM’s extensive use of CoC simplifies application code. Provided that GORM’s defaults for table and
column names match the schema, a class can be mapped
to the database schema with little or no configuration.
GORM also injects every domain class with primary-key
and version-number fields, which further reduces the
amount of coding required.
GORM has some limitations. It does not easily support
multiple databases. Dynamic finder methods cannot
have an intentional revealing name that encapsulates the
query. GORM lacks support for DAO classes, even though
complex applications might benefit from the improved
modularity that they offer. Applications that work with a
legacy schema will not be able to take advantage of CoC
since they require explicit configuration of ORM.
Despite these limitations, developers of a wide range of
applications will find GORM extremely useful. Developers
can use GORM independently of Grails but it is targeted
at Web application developers who can benefit from the
rapid development capabilities of the Grails framework.
In addition, GORM is best used when developing applications that access a single database or when using database
middleware that makes multiple databases appear as a
single database. Developers will get the most benefit from
GORM when they have control over the database schema
and can leverage GORM’s CoC features. Q
I would like to thank the following reviewers for the
helpful feedback on drafts of this article: Ajay Govindara-jan, Azad Bolour, Dmitriy Volk, Brad Neighbors, and Scott
Davis. I would also like to thank the members of the SF
Bay Groovy and Grails meet-up and the anonymous ACM
Queue reviewers who provided feedback on this article.
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CHRIS RICHARDSON is a developer and architect with
more than 20 years of experience. He is the author of POJOs
in Action (Manning Publications, 2006), which describes
how to build enterprise Java applications with POJOs and
lightweight frameworks. He runs a consulting and training
company that specializes in helping companies build better
software faster. He has been a technical leader at Insignia,
BEA, and elsewhere. Richardson has a computer science
degree from the University of Cambridge in England and
lives in Oakland, California. Web site and blog: www.chris-richardson.net.
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